Cleaning of coal



Jan. 17,1928.

v www l .E2 M m 3 n moz QSE Sm Patented 4.Ia-n. 417, 192s.

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. 1.656.211 f vuNI'li-:D STATES PATENT oFFlca. v

'POTTSVILLE PENNSYLVANIA, ASSIGNORS T0 HIRSCH-LEDERER SYNDICATE, DTC., F NEW YORK, N. Y., A CORPORATION 0F DELAWARE. y

CLEANING 0F coAL.

Appucaami mea xa'y s,

Our invention relates to the cleaning of coal. In order to remove slate and the like fromA coal it has been suggested that the coal v as it comes from .the mme be first screened to remove the so'cal1ed silt consisting largely of finelyl divided im urities, and then the mixture of coal and slate, etc., subjected to a gravity separation. For this purpose a fluid mass having a specific gravity intermediate .10 the specific gravity ofthe coal andthe specific gravity ofl the impurities, is `used-and the mixture su plied thereto whereupon the coal rises and ibats near the top of the fluid mass and the heavier impurities sink in the same. In order to provide such a fluid mass,

a mixture of water and sand has been suggested, the proportions of water andsand beingso adjusted as .to-bring the specific gravity of the ,fluid mass to a value between that of the Ispecific gravity of the coal and that of the specific gravity of the slate o r other impurities. The fluid mass is kept in a 'tation in order that the lspecific gravity olthe same may remain substantially uni- -form throughout the entire mass. The use of a dissolved soluble material to produce a fluid of suiiiciently high specific gravity to float the coal" and allow impurities such `as slate to sink hais been suggested, but has not proved commercially successful, and a fluid mass comprising a mixture of sandin water has proved the more advantageous. In such method the coal is drawn olat the top of the fluid mass with more orl less of the water and sand while the slate is drawn out separatelyfrom the bottom of the fluid mass also with considerable water and sand. Therefore, fresh sand and Water mustjbe continuously sup lied in order to keep the volume andspecifEic gravity of the fluid mass up to the vnecessary amount. The slate yor similar impurities which are drawn oil'l from the body of the fluid mass with considerable sand and water are separated therefrom by washing screensand the sand returned Vto the clyi'cle.v Also the coal which is drawn olf from t e top of the fluid mass with more or less of the sand and water, is separated therefromby washing screens and the sand returned to the cycle. In the coal to be with, 'there Y .is considerable finely divide coal or coal dust'and'dso a certain amount of degradation pf the coal takes place during theproc- 1925. Serial- No. 28,777.

ess which thus produces some finely divided coal, which is too fine to be separated froml the sand on the screens and passes through the screens with the sand. Therefore, this iinely divided coalv or coal dust is returned to the fluid mass along with the sand. As the iproportion of line coal or coal dust in the uid mass thus increases, a condition is reached where the specific gravity of the fluid mass (due to the accumulation of line coal therein of relativel low specific gravity) is reduced to a. point so that the fluid mass no. longer efficiently floats the coal in order to se arate it from the slate and similar impurities. practice at short intervals and after the fluid .mass has Vthus become degraded b the inclusion of line coal, to allow the uid mass containing sand and finely divided coal to y run to Waste and introduce freshclean sand to form the fluid mass, in order to maintain the properspecific gravit of the fluid mass.

The cost of such san replacement is a very important matter especially with coal which tends to form an appreciable amount of dust and also the finely divided coal or coal dust is lost. A similar loss of value also 0l' NEW HAVEN, CONNECTICUT, AND CHARLES H. STRANGE, 0F l Thereforeit has been the v takes place even if other materials or other liquids are used to produce the fluid mass. Ihe main object of our invention is to substantially avoid these losses and thus render the process less expensive and more eicient. For this purpose we propose to use as finely divided material to bring about the proper specific ravity in the fluid mass, inel divided so id matter which comes in'wit the coal, and Which'would otherwise go to waste, thus making the prociess far less expensive.

Further and more specific objects, features and advantages will more clearl appear from the detail description given elow taken in connection with the accompanying drawings which form a art of this specification. In the drawings, ig. l is avdiagram illustrating asystem for carrying out our 'improvements in one form thereof and Fig.

"2 .is a diagrammatic `detail illustrating a' modification.

Referring lto Fi 1 the run of mine coalvv Jpurities passes mto thehopper 8, while the" coal with such impurities as slate and the like is discharged into a chute 4 and into the conical gravity separator 6. The separator 6 is provided with stirring blades 7 operated by a shat't 8 in order to keep the mass in the separator 6 thoroughly agitated. The silt which is deposited in the hopper-. 3 is runthrough pipe 5 into the flotation cell or apparatus 19. This is provided with an agitator v2l in the lower part thereof whereby the mass is agitated in the bottom part of the cell, but suitable baille plates are provided whereby the mass in the upper part of the c'ell remains relatively quiescent. This flotation apparatus may, however, be of any suitable kind and operated in any other suitable manner, to separate from the silt finely divided coal which may remain therein after passing through the screen 2. This separation, however, is .preferably effected with the aid of a froth flotation agent. i. e., by the use of a relatively small quantity of oil or frothing agent as distinguished from the use of a relatively large quantity of oil, which latter method is commonly known in the art as bulk oil flotation, while the first method using a relatively small quantity of flotation agent is commonly known as froth flotation. However. the bulk oil flotation may be found advantageous in certain cases. Various selective agents may be used in the flotation aparatus such as insoluble collectors and solule frothing agents. Modifying agents such as organic compounds. acids. alkalis and salts may also be used to favorably affect the surfaces of the particles in or er that the finely divided coal will be more effectively preferentially floated from the rest. Air may be supplied to the flotation apparatus under pressure or may be beaten in by the action of agitators. We have found that' a combination of air under-pressure and mechanical agitation givesvery good results. The flotation step may be carried out under atmospheric pressure or under increased or diminished pressures. It is not `necessary to remove all of the finely divided Coal from the rest, atleast in most cases.

The degree of purity-of the recovered materialwill be governed by the special conditions controlling the coal washing in various cases. The frothing agent may be introduced at the bottom of the apparatus and alsoair under pressure may be intro-y duced at the bottom of the apparatus in order to aid in the separation. Likewise other chemicals maybe introduced to aid in the separation.

'The finely divided coal rises tothe top of the apparatus 19 and is removed or flows out over the to thereofand may be removed through t e trough 20. The remaining finely divided solids, thus freed of finchv divided coal, are removed from the bottom l of the cell 19 throuoh conduit 22 and fed onto screen 23 whicrh separates therefrom the particles which are too large for use in the gravity separator 6 and discharges them to waste down the chute 24. The smaller particles are deposited on the screen 25 which separates therefrom those of pro er size to be used in the se arator 6 and ischarges them onto the cinte 26 which de.- posits them in the settling tank 28. The iquid and matter too fine to be used in the separator 6 is discharged into hopper 27 and run to waste.

The finely divided solids with some water are pumped from the bottom of the tank 28 by means of pump 35 and forced up through pipe 36 and into the separator 6. lVater is introduced into the bottom of the separator 6 through pipe 10 and this water with the finely divided solid matter from pipe 36 forms a fluid mass therein which is ept in agitation by the stirring blades 7 and is of a specific gravity between that/of the coal and the slate etc. whereby the coal floats at the top part thereof and flows ofi through trough 9 and onto sizinflr screens 11, 13, 15, which separate the coal according to size and discharge the various sizes of coal onto chutes 12, 14 and 16 respectively.

Such finely divided solid matter and water as flow off with the coal and such finely divided coal as passes the screens 11, 13 and 15, is deposited in hopper 18 whence it flows back fto the flotation apparatus 19 by pipe 17, where it is subjected to the froth'orother flotation separation which removes the finely divided coal at the top and the other finely divided solids are returned to the screens 23 and 25 and to the tank 28 as before for I'GllSe.

The slate and similar impurities fall by gravity to the bottom of the separator 6 and with the gate valve 29 open, are deposited 1n the trap 30. Periodically the valve 29 is closed and valve 31. opened to permit the,

slate` etc. with some of the finely divided solid and water to fall upon the screen 32 which separates vthe slate etc. and discharges them on the chute 34 from 'which they are run to waste, while the finely divided solid ymatter and water pass the'screen 32 and are deposited in the hopper 33 from which they are run into the tank 28 to be reused like the finely divided solid matter and water received therein from the flotation apparatus `19. 'Excess water, with possibly some very finely divided solid matter, is run out of the tank 28 through the overflow 28.

Thus the finely divided solid matter which flows off with the coal at 9 is rei .los

turned to the flotation apparatus 19 where finely dividedcoal is separated therefrom and recovered. as a useful by-product, and the finely divided solid matter is then fed coal.

the separator 6, sand or other duced 40 and 41, the partl to the tank 28 whence it is pumped back through pipe 36 to be again used in the ravit separation of coal from slate, ctc. ikewise the finel divided solid matter escaping from the ottom of the separator 6 is discharged into the tank 28 to be ag in similarly returned and used in. the gravity separation. 1 v

The finely divided solid matter used to brin about the desired specific gravity'of the fuid mass in the separator 6 should have la greater specific gravity than that of the If the finely divided solid mattei' coming inf with the coalto betreated, is more than is needed for use in the separator 6, the excs may be removed from the tank .Y

28, or by running the discharge through pipe 17 to waste or the discharge from the opper 33 to waste, or otherwlse, or only part' of this material which is dischar ed into the hopper 3 may be fed to the flotation apparatus 19, the remainder being run to Waste. If the amount of finely divided solid mat-ter coming in with the coal is insufficient in weight or amount for the re uirements of nely divided solid matter from the neighborhood or else-V where may be added to makeup the deficiency. This may be added to` the tank 28 or directly to the separator 6. The amount of water introduced through the pipe 10 and ,the amount of finely divided solid intro-- is so regulated as to keep the specific gravity of the fluid mass at the desired or required value. In some cases the finely divided solid matter coming in with the coal may be run` directly into the separator 6 with the coal and .withoutfirst running it through the flotation apparatus 19, etc.

With regard to the finely divided solid matter which falls through the screens 11, 13fand 15, we believe th'at'most of the coal is found -at the right hand of the ho per 18 as viewed in Fig. solid mater substantially free from finely divided coal will be found in the left hand end 'of the hopper.I Therefore, the latter portion may need notreatment in the fiotation apparatus and in. order to avoid Waste of energy etc. in purifying this, the arrangement illustratedmin Fig. 2 may be used wherein the hopperis divided into two arts 40 catching thev nely divided solid matter which contains most of the finely divided coal and returningy it through pipe 17 to the flotation apparatus 19 for separation etc. while the finely divided solid matter which is substantially free of finely divided coal is dischargeddirectly to the tank 28 by pipe 42.

In our copending application Ser. No. 28,776 filed May 8, 1925,` vwe have described and claimed broadly the use of a finely divided Solid in suspension for producing gravity separation of the coal and the with l for further water, nevertheless, any other 1, while finely divided' ratus may be screened before instead'o U4 drawing of finely divided solid gravity separation and treating it to remove therefrom andreturning the cleaned solid ravity separation of coal, and' we do not c aim the same broadly herein, this application bein directed specifically to the use of finely inwith the coal for thereof.

The invention may be agiplied to the treatment of a great variety o coals and also for the separation therefrom of many other impurities and slate. Itmay be alp lied to the recovery ofcoal orsimilar fue rom waste dum s of various kinds, and b the. term coag we include such similar uel as coke and the like.

While we have mentioned the use of screens such as 32 forseparating slate from the fine solid material and water/and screens such as 11, V13 and 15 for separatingthe sized lcoal from the fine solid material and suitable separatin or classifying apparatus or devices may ie used for these pu ses. Likewise any other suitable form o fiotati'on appa the gravity separation from the..

Afinely divided coal and other impurities ivided matterv coming 'i rat-us may be used, and other forms of ap- .be subjected to the action of a plurality of screens, the top one passing all coal including pea size and smaller andthe lower one passlngbnly the silt. The coal above pea size may go directly to the separator 6and likewise one-half the coal held on the silt removing screen.' The other half of the latter may be mixed, without cleaning, with the discharge from the separator at 9. If desired soluble material may be dissolved in the water in, or supplied to, the separator 6 to aid in increaslng the specific gravity thereof. If too much water is returned to the flotation apparatus through pipe 17, a settlin tank may be introduced to remove part 0% the water before the material isin- "'troduce-d into the flotation apparatus. Or

if necessary more water may be added "to the pipe 17 The silt fed to the otation a pta'- y the screens -23 and 25 afterward. Also many other changes and modifications may bemade and the invention mnbodied in widely different forms without departin and scope thereof in its -roader aspects'. Hence we desire to cover'all forms and modifications coming within the .y language or scope of any one or more of the appended claims. f What we claim as new and desire to secure .by Letters. Patent is 1 consists in separating impurities from the coal by gravity in a liquid having' finely divided solid matter in suspension therein,

from the spirit l. The method, of cleaning coal which -lio to form a fluid mass having a specific gravity between that of the coal and the impuri- -ties to be separated therefrom, said finely divided matter comprising in a large measure, finely divided solid matter found with the coal, withdrawing finely divided solid matter from the gravity separation and treating it by fiotation to remove finely divided coal therefrom, and returning the solid matter from which finely divided coal has been thus removed by fiotation, for further gravit.' separation of coal from impurities.

2. 'l 1e process of' cleaning coal which oonsists in separating therefrom impurities of higher specific gravity than the coal, by gravity in a iuid having a specific gravity between that of the coal and that of the impurities, the fluid mass being agitated and comprising water carrying in suspension finely divlded solid matter, sald finely divided solid matter comprising. in a large measure, finely divided solid matter found with the eoal, withdrawing finely divided solid matter from said gravity separation step, and treating the same by froth fiotation to remove finely divided coal therefrom, and returnino` the solid matter from which finely ldividedcoal has been thus removed by fiotation, for further gravity separation o coal from impurities. i

3. The process of cleaning eoaleontaining substantial quantities of finely divided impurities of higher specific gravity than the coal, which consists in feeding the impure coal into an agitated fluid mass comprising water and fineljy divided solid matter in suspension therein, whereby said finely divided impurities aid in forming a fiuid mass of sueh specific gravity that the coal will float in the upper part of said mass and slate or the like will sink to the lower part of said mass, removing purified coal from the top of the mass, separating therefrom finely 'divided solid matter which is removed therewith, subjecting the finely divided solid matter to froth flotation to separate therefrom finely divided coal which is retained therein from the gravity separation, and returning the solid matter from which finely divided coal has been thus removed by flotation, for further gravity separation of coal from impurities;

In testimony whereof we have signed our names to this specification.

CHARLES R. ADOWNS. CHARLES H. STRANGE. 

